CN112639044A

CN112639044A - Compostable hot melt adhesive

Info

Publication number: CN112639044A
Application number: CN201980058092.XA
Authority: CN
Inventors: M·D·坎德斯基; M·D·维特拉诺; D·P·基勒; D·普坦普尔比奥; J·M·兰伯特; B·J·莫罗
Original assignee: Bostik Inc
Current assignee: Bostik Inc
Priority date: 2018-09-07
Filing date: 2019-09-06
Publication date: 2021-04-09
Also published as: WO2020051422A1; US11661537B2; MX2021002642A; US20230313004A1; EP3847222A1; JP2024028774A; JP7394841B2; JP2021536524A; US20200079981A1; KR20210056389A

Abstract

A hot melt adhesive comprising: polylactide homopolymers or copolymers, such as polylactic acid; sulfonated copolyesters; and at least one plasticizer; and is compostable. The plasticizer may be a solid plasticizer, such as benzoate, and a secondary plasticizer may also be used. The adhesives are suitable for use in a variety of applications, such as case and carton applications, with burlap or other compostable substrates for tree bulbs or plant seeds, and with other compostable films, and are particularly suitable for use in double-walled cardboard drinking cups. The adhesive exhibits good cohesive properties comparable to non-compostable adhesives over a temperature range that reflects the temperature of hot and cold beverages.

Description

Compostable hot melt adhesive

Cross Reference to Related Applications

The present application claims benefit of U.S. patent application No. 62/728,424 filed on 2018, 9, 7, 35u.s.c. § 119 (e).

Technical Field

The present invention relates to a hot melt adhesive that can be composted and is particularly suitable for use as an adhesive for paperboard beverage cups for both hot and cold beverages.

Background

Hot melt adhesives are used in a variety of commercial applications. One advantage of hot melt adhesives is that these systems do not require a carrier fluid or solvent for application to the substrate, and thus eliminate the need for subsequent evaporation of the solvent or carrier fluid. The absence of a drying or evaporation step allows the hot melt adhesive system to eliminate the hazards associated with the use of solvents and the environmental impact of Volatile Organic Compounds (VOCs). The use of hot melt adhesives also reduces water consumption since water is not required as part of the adhesive. Hot melt adhesive formulations can vary over a wide range of adhesive properties, from pressure-sensitive to non-pressure-sensitive.

Hot melt adhesives are traditionally based on petroleum based polymers. Thermoplastics have been used as the polymeric component of hot melt adhesives and are generally classified into three types: (1) petroleum-based polymers such as polyethylene, polypropylene, ethylene-vinyl acetate, styrene block copolymers (e.g., styrene isoprene styrene, styrene butadiene styrene); (2) a polyurethane; and (3) polyester/polycarbonate materials.

Many of these products suffer from poor environmental degradability. There is a strong demand for packaging materials in which renewable resource materials like paper, starch and certain degradable plastics (aliphatic polyesters, polylactides, etc.) are used. In the case of paper products, the use of environmentally degradable binders will allow the adhesive to be composted when the paper, paperboard or cardboard product is recycled. Or alternatively, the use of an environmentally degradable adhesive will render the entire assembled article compostable, unlike articles sealed with typical petroleum-based hot melt formulations.

Some adhesive applications have more demanding requirements than others, and adhesives that are compostable and used in paperboard drinking cups must perform several functions. For an adhesive to be used for sealing cardboard beverage cups, it must be capable of acting as an adhesive over a range of temperatures, given that the cup may contain a cold beverage, such as juice or soda, or a hot beverage, such as coffee or tea. For example, the adhesive must meet performance requirements where the cup is filled with hot water (e.g., about 180 ° F-190 ° F) and tears, then the result must be 100% fiber tear on all seals (both radial and end seals) of the adhesive. In other words, there must be no cohesive or adhesive failure; the cup must first tear. In addition, this test must pass both after initial (off-line) and after aging conditions (i.e., 5 days at 72 ° F). Furthermore, the adhesive must be compostable without compromising its bonding properties. Furthermore, it is desirable to allow the hot melt adhesive to run on existing hot melt adhesive application equipment, which means that it must have similar flow characteristics, including viscosity, at the application temperature.

Hot melt adhesives have been used to bond together the outer wall of disposable paper cups used to hold beverages such as coffee or tea and another substrate (e.g., paper/label) that serves as the second wall. To bond the cup to the label, it is known to apply a plurality of radial beads of hot melt adhesive around the periphery of the cup, and to apply a seaming bead (or end seal) along the length of the cup where the edges of the label meet. There are no compostable hot melt adhesives known in the market today that have acceptable heat resistance for hot beverage conditions (e.g., at 180 ° F-190 ° F). There are also no compostable hot melt adhesives known in the market today that have a wide range of use temperatures, e.g., (0F. -160F.).

U.S. patent No. 5,753,724 discloses hot melt adhesive compositions made using polyesters derived from lactic acid. The thermoplastic resin grade polyester is formulated into a functional adhesive using an adhesive component. In formulated hot melt adhesives, lower molecular weight materials may be used as tackifying resins with the biodegradable/compostable resins. By combining the polyester polymer with other biodegradable/compostable components, the adhesive material can be made pressure sensitive and can be made fully degradable. The resulting adhesive composition may be used in a variety of applications. Biodegradable/compostable binder materials can be used as a substitute for non-biodegradable materials made from commercial polymers that are resistant to attack by bacterial, fungal and other microbial populations. Hot melt adhesives are useful for packaging and manufacturing disposable articles made from degradable materials. The entire disposable article may be made of fully compostable adhesives and structural materials.

Us patent No. 7,868,101 discloses a process for preparing environmentally degradable polymers, as well as such compounds themselves and their use. The compounds of the present invention include polycondensation lactic acid containing polymers having a molecular weight (Mw) of from 500 to 50,000g/mol coupled with a toughening aliphatic polyester having a molecular weight of from 500 to 50,000 g/mol. The amount of groups including lactic acid in the polymer ranges from 50% to 99%, and the amount of toughening polyester groups ranges from 1% to 50%.

Disclosure of Invention

Embodiments of the present invention avoid many of the problems and limitations of the prior art. One embodiment of the present invention is directed to a compostable hot melt adhesive suitable for use in a variety of applications, such as case and carton (carton) applications, and particularly suitable for use in double wall paper board cups. The hot melt adhesive composition of this embodiment comprises: polylactide homopolymers or copolymers; sulfonated copolyesters; and a plasticizer; and is compostable. The polylactide homopolymer or copolymer may be selected from the group consisting of: polylactic acid; and copolymers of lactones, preferably glycolide and caprolactone. The plasticizer is preferably solid and may comprise a benzoate ester, preferably 1, 4-cyclohexanedimethanol dibenzoate. The adhesive composition may include a second plasticizer, which may be selected from at least one of ethylene glycol, propylene glycol, and polyethylene glycol. The adhesive composition may also include an antioxidant, such as a hindered phenol. In an embodiment, the adhesive composition comprises no more than 5 wt%, more preferably no more than 4 wt%, and most preferably no more than 3 wt% of ingredients having a hydroxyl number greater than 100mg KOH/g.

According to another embodiment of the invention, a method for forming a double-walled container comprises the steps of:

(a) applying the hot melt adhesive composition of the invention described herein in a molten state to the outer surface of a first generally cylindrical paperboard substrate;

(b) splicing a second generally rectangular paperboard substrate to the first paperboard substrate, wherein the second paperboard substrate is longer than the perimeter of the first paperboard substrate, thereby providing an overlapping end axial strip of the second paperboard substrate; and

(c) applying the hot melt adhesive composition in a molten state to one of the running surfaces of the axial strips; and

(d) splicing the splicing surfaces of the axial strips to provide the double-walled container.

Another embodiment of the present invention is directed to a container formed by the method of the present invention as described herein. In an aspect of this embodiment of the invention, the paperboard for the container is compostable and the container is a beverage cup.

Embodiments of the present invention provide a compostable hot melt adhesive having bonding properties and heat resistance characteristics similar to conventional non-compostable hot melt adhesives, such as those based on polyolefins, ethylene vinyl acetate, or styrene block copolymers. The adhesives according to the invention may be used in a variety of end uses, such as case and carton applications, with compostable films, with tree bulbs (bulbs) or plant seeds wrapped in burlap (burlaps) or other compostable substrates, and in the construction of various articles, such as double-walled drinking cups. With respect to its use in the construction of a compostable double wall beverage cup, the adhesive may be used to bond together the outer wall of the inner base of the disposable paper cup and another outer base (e.g., paper/label) that serves as the second wall. Alternatively, the same adhesive may be used to bond the inner substrate to the outer substrate and to bond the outer substrate to itself at the end seal region of the second wall.

Other features and advantages of the present invention may be apparent to those of ordinary skill in the art upon reading the following description.

Detailed Description

According to embodiments of the present invention, a hot melt adhesive composition is compostable and comprises a polylactide homopolymer or copolymer; sulfonated copolyesters; and a plasticizer.

The polylactide homopolymer or copolymer is selected from the group consisting of: polylactic acid; and copolymers of lactones, preferably glycolide and caprolactone. In a preferred embodiment, the polylactide homopolymer or copolymer comprises, consists essentially of, or consists of polylactic acid. In other embodiments, the polylactide homopolymer or copolymer has a melt index of at least 50g/10min, preferably at least 55g/10min, and most preferably at least 60g/10min using a 2.16kg weight at 210 ℃ according to ASTM method D1238. The polylactide homo-or copolymer has a melt index according to ASTM method D1238 at 210 ℃ using a 2.16kg weight of at most 500g/10min, preferably at most 200g/10min, more preferably at most 150g/10min, and most preferably at most 100g/10 min.

In an embodiment, the polylactide homopolymer or copolymer comprises at least 20 mole percent lactide comonomer. The general structure of polylactide is shown below:

suitable polylactide homopolymers or copolymers for use herein may have a number average molecular weight in the range of 3,000 to 200,000 g/mol(s) ((R))Mn). (all molecular weights mentioned herein are measured by Gel Permeation Chromatography (GPC) using polystyrene standards.) although poly (D, L-lactide) and meso-are substantially amorphous, poly (L-lactide) and poly (D-lactide) are crystalline in nature and have crystalline melting points of 186 ℃ depending on their molecular weight and stereo purity. The polymers may be prepared by using acid or base catalysts such as PbO, SnCl₂、SnCl₄、ZnCl₂、SbF₅、Sb₂O₃Or the bimolecular cyclic ester of lactic acid of triethylamine, using solution, precipitation or melt methods. Alternatively, they may be obtained from Henley Chemicals, Inc

Trade names are commercially available; commercially available from Polymer science Inc. (Poly Sciences Inc.) or eco-Chemical Products Company (Ecologic Chemical Products Company, EcoChem).

In addition to homopolymers of poly (L-lactide), poly (D, L-lactide), and poly (meso-lactide) are polylactide homopolymers or copolymers suitable for use herein, and may also be prepared by copolymerization with other lactones, such as glycolide or caprolactone. Poly (D, L-lactide-co-glycolide) polymers containing equimolar amounts of lactide and glycolide components are available from Henry Chemicals, Inc

RG502, 503, 504, 505, and 506 are obtained and are suitable for use herein. In addition, poly (D, L-lactide-co-glycolide) polymers comprising 75% lactide component (referred to as

RG752, 755, and 756) and containing 85% lactide

858 polymers are also suitable.

In one embodiment, the polylactide homopolymer or copolymer is a thermoplastic resin derived from a renewable resource. Preferably, the polylactide homo-or copolymer is amorphous and has a low melting point. In embodiments of the invention, the polylactide homo-or copolymers have a specific gravity according to ASTM D792 of between about 1.1 and about 1.5, preferably between about 1.15 and about 1.4, and most preferably between about 1.2 and about 1.3. In embodiments of the invention, the glass transition temperature of the polylactide homopolymer or copolymer is between about 40 ℃ and about 70 ℃, preferably between about 45 ℃ and about 65 ℃, and most preferably between about 50 ℃ and about 60 ℃ according to ASTM D3417. In embodiments of the present invention, the melt index of the polylactide homopolymer or copolymer is at least about 50g/10min using a 2.16kg weight at 210 ℃, preferably at least about 55g/10min using a 2.16kg weight at 210 ℃, and most preferably at least about 60g/10min using a 2.16kg weight at 210 ℃; and which has a melt index of at most about 500g/10min at 210 ℃ using a 2.16kg weight, preferably at most about 200g/10min at 210 ℃, more preferably at most about 150g/10min at 210 ℃, and most preferably at most about 100g/10min at 210 ℃, all according to ASTM method D1238. In all instances herein, when multiple values are provided for a lower limit and multiple values are provided for an upper limit of any characteristic or concentration range, the present invention contemplates any range extending from and including any lower limit to and including any upper limit.

An exemplary polylactide homopolymer or copolymer is the Vercet series of resins, particularly Vercet a1000, which is commercially available from nychiwalk LLC (Nature Works LLC). This is a thermoplastic resin derived from annually renewable resources, obtained in particulate form, and is an amorphous, low melting, high flow resin.

The hot melt adhesive composition also comprises a sulfonated copolyester. In embodiments of the invention, the sulfonated copolyesters have specific gravities of about 1 to about 1.5g/cm according to ASTM D792³Between about 1.1 and about 1.3g/cm, preferably³And most preferably between about 1.2 and about 1.3g/cm³In the meantime. In bookIn embodiments of the invention, the glass transition temperature of the sulfonated copolyester is between about 30 ℃ and about 70 ℃, preferably between about 35 ℃ and about 60 ℃, and most preferably between about 40 ℃ and about 50 ℃ as tested using DSC (according to ASTM E1356-08), where the inflection point, i.e., the midpoint of the bend (second-order transition) during the second thermal cycle, is determined. In embodiments of the present invention, the intrinsic viscosity of the sulfonated copolyester is between about 0.15dl/g and about 0.45dl/g, preferably between about 0.2dl/g and about 0.4dl/g, and most preferably between about 0.25dl/g and about 0.35dl/g, according to ASTM D5225-14. In embodiments of the present invention, the acid number of the sulfonated copolyester is zero or at least about 0.01mg KOH/g and preferably at least about 0.1mg KOH/g, and up to about 10mg KOH/g, preferably up to about 5mg KOH/g, and most preferably up to about 3mg KOH/g. In embodiments of the present invention, the sulfonated copolyesters have a hydroxyl number of zero or at least about 0.01mg KOH/g and preferably at least about 0.1mg KOH/g, and up to about 15mg KOH/g, preferably up to about 10mg KOH/g, and most preferably up to about 5mg KOH/g. In embodiments of the present invention, the sulfonated copolyester has a weight average molecular weight between about 20,000g/mol and 80,000g/mol, preferably between about 25,000g/mol and 60,000g/mol, and most preferably between about 28,000g/mol and 42,000 g/mol. The viscosity of the polyester is preferably between 1000cP and 100,000cP, most preferably between 5000 and 60,000cP at 350 ℃ F. The viscosity was measured in a brookfield viscometer using a #27 spindle. Viscosity is generally related to molecular weight, with higher viscosity corresponding to higher molecular weight.

According to embodiments of the present invention, the sulfonated copolyesters may be selected from those described in U.S. Pat. No. 6,410,627, which is incorporated herein by reference. This patent describes polycondensates comprising the reaction product of:

a. at least one difunctional dicarboxylic acid which is not a sulfomonomer or the corresponding methyl ester;

2 to 25 mole percent of at least one sulfomonomer comprising at least one metal sulfonate group or nitrogen-containing non-metal sulfonate group attached to an aromatic or cycloaliphatic core, and at least one functional group selected from the group consisting of: hydroxyl, carboxyl and amino;

c. at least one difunctional reactant selected from the group consisting of a diol or a mixture of a diol and a diamine having two-NRH groups, said diol containing two-C (R1) 2-OH groups, wherein R in the reactant is hydrogen or an alkyl group of 1 to 6 carbon atoms, and R1 in the reactant is a hydrogen atom, an alkyl group of 1 to 5 carbon atoms, or an aryl group of 6 to 10 carbon atoms;

0 to 40 mole percent of a difunctional reactant selected from the group consisting of hydroxycarboxylic acids having one-C (R) 2-OH group, aminocarboxylic acids having one-NRH group, aminoalcohols having one-C (R) 2-OH group and one-NRH group, or mixtures of said difunctional reactants, wherein R in the reactants is hydrogen or alkyl of 1 to 6 carbon atoms; and

e.0 to 40 mole percent of a polyfunctional reactant having at least three functional groups selected from the group consisting of hydroxyl groups, carboxyl groups, and mixtures thereof, wherein at least a portion of the polyfunctional reactant has at least three hydroxyl groups,

wherein all of the stated mole percentages are based on the sum of all of the acid, hydroxyl, and amino containing reactants (equal to 200 mole percent), and wherein the polymer comprises the ratio of the acid group containing reactant (100 mole percent acid) to the hydroxyl and amino containing reactant (100 mole percent base) such that the value of (equivalent) EQ (base) divided by (equivalent) EQ (acid) is between 0.5 and 2. The polyester composition used as a component of the hot melt adhesive of the present invention preferably comprises 60 to 100 mole percent of (a), 4 to 20 mole percent of (b), 80 to 100 mole percent of (c), 0 to 10 mole percent of (d) and 0 to 20 mole percent of (e). In other more preferred embodiments of the present invention, the polyester comprises 60 to 100 mole percent of 1, 4-cyclohexanedicarboxylic acid; 4 to 20 mole percent of 5-sodiosulfoisophthalic acid or dimethyl 5-sodiosulfoisophthalate; and 80 to 100 mole percent diethylene glycol, neopentyl glycol, or cyclohexanedimethanol.

According to embodiments of the present invention, the sulfonated copolyesters may be selected from those described in U.S. patent nos. 4,910,292, 4,973,656, and 4,990,593, which are incorporated herein by reference. In the inventionIn yet another embodiment, the sulfonated copolyesters include those commercially available from Bostik rubber company (Bostik, Inc.)

1831044 copolyester polymer. Sulfonated copolyester based hot melt adhesives are described in U.S. patent No. 5,750,605, which is incorporated herein by reference. Exemplary sulfonated copolyesters also include the Eastman AQ series of solid copolyesters commercially available from Eastman Chemical company (Eastman Chemical).

In embodiments of the present invention, the sulfonated copolyesters are water dispersible. Water dispersibility can be measured by the ability of the resin to disperse and remain as a uniform dispersion after mixing. This characteristic can be determined by combining the product with water under heat (e.g., 95 ℃) and applying shear. The resin softens first when heated (i.e., it is transparent and amorphous and then becomes cloudy and soft when mixed with water). Once mixing is complete, the product is said to be water dispersible if it does not settle or phase separate under gravity.

The use of sulfonated copolyesters offers the additional advantage of providing a degree of water sensitivity, which is dependent on the ionic strength of the aqueous environment. Thus, adhesives can be formulated that are sufficiently resistant to the ionic environments encountered during use (e.g., exposure to body fluids encountered in diapers and feminine sanitary napkins), but still disperse and/or debond in tap water having a relatively low ionic strength. Thus, these binders are particularly useful in the construction of compostable articles.

The hot melt adhesive composition further comprises a plasticizer. Preferably, the plasticizer is a solid plasticizer, which is particularly useful in embodiments where high heat resistance is required. The solid plasticizer may include benzoate. The benzoate ester may be selected from the group consisting of: glycerol tribenzoate, sucrose benzoate, pentaerythritol tetraphenyl formate and 1, 4-cyclohexanedimethanol dibenzoate. Most preferably, the benzoate esters include, consist essentially of, or consist of 1, 4-cyclohexanedimethanol dibenzoate, which is commercially available from Istman chemical company under the trademark Benzoflex 352. One of the drawbacks of using polylactide homopolymers or copolymers is poor heat resistance properties. It has been found that incorporating a solid plasticizer into the formulation provides the heat resistant characteristics needed for use as an adhesive for disposable cups for hot beverages. Vegetable wax-based solid plasticizers may also be suitable.

In one embodiment, the solid plasticizer has a melting point between about 80 ℃ and about 160 ℃, preferably between about 90 ℃ and about 150 ℃, more preferably between about 100 ℃ and about 140 ℃, still more preferably between about 110 ℃ and about 130 ℃, and most preferably between about 110 ℃ and about 125 ℃ using DSC according to ASTM D7138. In embodiments of the invention, the acid number of the solid plasticizer is zero or at least about 0.001mg KOH/g and preferably at least about 0.01mg KOH/g, and up to about 3mg KOH/g, preferably up to about 1mg KOH/g, and most preferably up to about 0.2mg KOH/g. In embodiments of the present invention, the sulfonated copolyesters have a hydroxyl number of zero or at least about 0.01mg KOH/g and preferably at least about 0.1mg KOH/g, and up to about 10mg KOH/g, preferably up to about 5mg KOH/g, and most preferably up to about 3mg KOH/g.

In an embodiment of the invention, the adhesive further comprises a second plasticizer. The second plasticizer is selected from the group consisting of: ethylene glycol, propylene glycol and polyethylene glycol. Polyethylene glycol (e.g., PEG 400) having a lower viscosity is used to reduce the viscosity of the adhesive. Liquid plasticizers are particularly advantageous in embodiments where a solid plasticizer is used as the first plasticizer and a reduction in formulation viscosity is desired. A range of polyethylene glycols may be used depending on the desired viscosity of the formulation.

Other plasticizers suitable for use in hot melt adhesive compositions are described in U.S. patent No. 5,753,724, which is incorporated herein by reference. The plasticizer can improve the melting property of the adhesive, can impart pressure-sensitive properties, can expand the adhesive to reduce the cost, and can increase the flexibility and melting property of the hot-melt adhesive. Preferred plasticizers for use with the hot melt adhesives of the present invention are biodegradable/compostable plasticizers. Such plasticizers typically include natural cycle oils or manufactured synthetic materials containing ester groups or urea carbamoyl or amide groups. Plasticizers typically have a different molecular weight than the other components of the adhesive composition. When a solid plasticizer is used as the first plasticizer and it is desired to reduce the viscosity of the formulation, a liquid plasticizer, such as a material having a molecular weight of less than about 5,000g/mol, preferably less than 1,000g/mol, is used, which can provide the plasticizer characteristics to the compositions of the present invention. Preferred classes of plasticizer materials for use in the present invention include natural fats and oils that are compatible with the other ingredients disclosed herein. Another class of preferred plasticizers for use in the adhesives of the present invention include ester plasticizers, which are typically made by reacting an aromatic or aliphatic small molecule mono-, di-, or triol with an aromatic or aliphatic acid composition. Specific examples of additional plasticizers include castor oil, TegMer 809-PEG 400 di-2-ethylhexanoate, Plasthall DBS-dibutyl sebacate, Plasthall DIBA diisobutyl sebacate, Santizer 160 (which is butyl benzyl phthalate), polycaprolactone diol having a molecular weight of about 500 grams/mole and a melting point below about 25 ℃, ethylene glycol dibenzoate, propylene glycol dibenzoate, diethylene glycol dibenzoate, and dipropylene glycol dibenzoate.

In embodiments of the invention, the adhesive further comprises a stabilizer or antioxidant. Stabilizers/antioxidants useful in the hot melt adhesive compositions of the present invention are incorporated to help protect the other ingredients noted above, and thus the overall adhesive system, from thermal and oxidative degradation that typically occurs during manufacture and application of the adhesive, as well as during ordinary exposure of the final product to the ambient environment. The antioxidant may comprise a hindered phenol. The hindered phenol may be selected from the group consisting of: 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene; pentaerythritol tetrakis-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate; n-octadecyl 3, 5-di-tert-butyl-4-hydroxyphenyl) propionate; 4,4' -methylenebis (2, 6-di-tert-butylphenol); 4,4' -thiobis (6-tert-butyl-o-cresol); 2, 6-di-tert-butylphenol; 6- (4-hydroxyphenoxy) -2, 4-bis (n-octylthio) -1,3, 5-triazine; di-n-octadecyl-3, 5-di-tert-butyl-4-hydroxybenzylphosphonate; 2- (n-octylsulfanyl) -ethyl 3, 5-di-tert-butyl-4-hydroxybenzoate; and sorbitol hexa [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ]. The hot melt adhesives of the present invention may also contain stabilizers and/or antioxidants in an effective amount, preferably in an amount of from about 0.1% to about 5% by weight. Preferably, from about 0.1% to 2% of a stabilizer or antioxidant is incorporated into the composition. Among the applicable stabilizers are hindered phenols and multifunctional phenols such as sulfur and phosphorus-containing phenols.

Polyolefin nucleating agents may also be present in the adhesives of the present invention. Nucleating agents suitable for use in the present invention are generally a subclass of nucleating agents known as clarifying agents, which are commonly used in polyolefin additive packages to promote rapid crystallization. Suitable materials include dibenzylidene sorbitol derivatives such as Millad 3988 and Millad NX8000 supplied by Milliken & company (Milliken) and Irgaclear D produced by BASF. Other suitable agents include aromatic amide systems such as NJ Star NU-100 supplied by New Japan Chemical Company. If included, the nucleating agent is typically present in the adhesive composition in an amount of about 0.05% to 5% by weight of the composition, preferably about 0.1% to 2.5% by weight, and most preferably about 0.2% to 1.0% by weight is used. Blends of two or more nucleating agents may also be used. For example, a blend of a nucleating agent and a second nucleating agent that is different from the first nucleating agent may also be used. If desired, from about 0.05% to about 5% by weight of one or more additional nucleating agents may be blended with the first nucleating agent. The nucleating agent may be used directly as a powder, or as a slurry in a portion of a suitable plasticizer, or as a component in a masterbatch of a suitable polymer masterbatch (e.g., Milliken NX-10). Nucleation packages (Nucleation packages) such as those described in US 2015/0299526 may also be included to tailor the setting rate and bonding characteristics of the hot melt adhesive.

It is to be understood that other optional additives may be incorporated into the adhesive compositions of the present invention in order to alter specific physical properties. These may include, for example, materials such as Ultraviolet (UV) absorbers, waxes, surfactants, inert colorants, titanium dioxide, fluorescers, and fillers. Typical fillers include talc, calcium carbonate, clay silica, mica, wollastonite, feldspar, aluminum silicate, alumina, hydrated alumina, glass microspheres, ceramic microspheres, thermoplastic microspheres, barite and wood flour and may be included in amounts up to 40% by weight, and preferably between 1 and 30% by weight.

The binders of the present invention are compostable. As used herein, the term "compostable" as applied to an adhesive is an adhesive that meets the following requirements: (1) decomposition testing as defined by ASTM D6400-12 (using ISO 20200) (84 days compost exposure) or (2) aerobic biodegradation as defined by ASTM D6400-12 (using ASTM 5338-15) (141 days at 58. + -. 2 ℃). In other words, the binder will achieve a minimum of 90% weight loss within 84 days under the decomposition test conditions, or will achieve at least 90% carbon conversion (based on CO) within 141 days according to the aerobic biodegradation test described in more detail in the examples₂Generation). In a preferred embodiment, the adhesive meets the following two requirements: (1) decomposition test as defined by ASTM D6400-12 (using ISO 20200) (84 days compost exposure) and (2) aerobic biodegradation as defined by ASTM D6400-12 (using ASTM 5338-15) (141 days at 58. + -. 2 ℃).

It has been found that the relative amounts of the various ingredients are important to the adhesive to achieve the various properties required for the desired application. It has been found that this is particularly true when an adhesive is used to seal two walls together in a drinking cup, which requires heat resistance, resistance over a wide temperature range, and compostability. In embodiments, the polylactic acid, the sulfonated copolyester, and the plasticizer are present in amounts effective to achieve at least 80%, preferably at least 90%, and most preferably 100% bonding performance. As used herein, "bond performance" refers to the adhesive performance when applied to uncoated paperboard and tested in the following manner: corrugated flaps (corrugated flaps) were cut into 1.5 "x 4" samples. The adhesive was applied as a 3/8 "bead at 350 ° F with an open time of 2 seconds and a compression time of 2 seconds. The cement was allowed to stand at room temperature overnight. Three bonds made with each adhesive were placed in a 0 ° F freezer and 160 ° F oven for 24 hours. At that time, the bonds were tested for percent fiber tear immediately after removal. "fiber tear" refers to the area of the substrate that is torn, as opposed to the area where the adhesive fails, whether adhesive or cohesive. In a preferred embodiment, the polylactic acid, sulfonated copolyester, and solid plasticizer are present in amounts effective to achieve the above-described bonding properties at a temperature of about 175 ° F, most preferably in the temperature range of from 0 ° F to 175 ° F. In other embodiments, wherein the polylactic acid and the sulfonated copolyester are present in a weight ratio of between about 1:1 and about 9:5 by weight, preferably between about 6:5 and about 8:5 by weight, and most preferably between about 13:10 and about 3:2 by weight.

According to an embodiment of the invention, the formulation comprises about the following ingredients in the following weight percentages:

polylactic acid is present in an amount to serve as a base polymer to provide cohesion to the adhesive, and in embodiments is present in an amount between about 25% and about 43% by weight, preferably between about 30% and about 38% by weight, and most preferably between about 31% and about 37% by weight;

the sulfonated copolyester is present in an amount effective to act as an adhesion promoter to a porous substrate such as paperboard or label, and in embodiments is present in an amount between about 15% and about 35% by weight, preferably between about 20% and about 30% by weight, and most preferably between about 22% and about 28% by weight;

plasticizers are present in an amount effective to increase the heat resistance of the formulation to a desired level (e.g., to the above-mentioned bonding properties at high temperatures), and in embodiments in an amount of between about 5% and about 60% by weight, preferably between about 15% and about 55% by weight, more preferably between about 20% and about 50% by weight, and most preferably between about 36% and about 42% by weight; and

if used, the second plasticizer is present in an amount effective to reduce the viscosity of the adhesive to the desired value, and in embodiments is present in an amount between about 1% and 5% by weight, preferably between about 1.3% and about 3% by weight, and most preferably between about 1.5% and about 2% by weight.

If used, the antioxidant (e.g., hindered phenol) is present in an amount effective to prevent oxidation or stabilize the adhesive, and in embodiments is present in an amount between about 0.1% and about 1% by weight, preferably between about 0.25% and about 0.75% by weight, and most preferably between about 0.4% and about 0.6% by weight.

Preferably, the composition comprises no more than 5 wt%, more preferably no more than about 4 wt%, and most preferably no more than about 3 wt% of ingredients having a hydroxyl number greater than 100mg KOH/g. Such ingredients may be, for example, styrene allyl copolymers, neopentyl glycol phthalate, polyester polyols, or combinations thereof, as disclosed in U.S. patent No. 6,410,627, which is incorporated herein by reference.

There is no particular order in making the adhesive composition of the invention, and it may be made using conventional process steps. The adhesive may be manufactured by mixing the various ingredients and then heating just prior to application to the substrate.

The viscosity of the adhesive material according to the invention should generally be at an application temperature suitable for processing and application to its substrate as a hot melt adhesive. Adhesives having a relatively low viscosity at low application temperatures require processing through standard hot melt adhesive equipment and achieve the desired pattern and thus suitable bonding properties at the application temperature. Generally, the viscosity is equal to or less than about 50,000cP at the application temperature, preferably equal to or less than about 40,000cP at the application temperature, even more preferably less than about 35,000cP at the application temperature, and still more preferably less than about 30,000cP at the application temperature, according to ASTM D3236. All viscosities identified herein are measured according to this modified ASTM standard. Preferably, the viscosity of the composition is at least 1,000cP, more preferably at least 5,000cP, still more preferably at least about 7,500cP, and most preferably at least about 15,000cP at the application temperature. Thus, at 121 ℃, the viscosity can be between 1,000cP and 35,000cP and between 5,000cP and 20,000 cP. In other embodiments, the viscosity of the composition at various typically used application temperatures, the values of which depend on the particular application of the adhesive, are between 121 ℃ and 180 ℃, such as at 121 ℃, 127 ℃, 135 ℃, 149 ℃, and 177 ℃, between any of the ranges contemplated herein. In embodiments where the adhesive is used to bond double wall cups for hot beverages, the viscosity of the adhesive at 177 ℃ is preferably between about 5,000cP and about 50,000cP, more preferably between about 15,000cP and about 35,000cP, and most preferably between about 20,000cP and about 30,000 cP.

End-use application requirements are important considerations in identifying the desired softening point of the adhesive formulation. For applications where an adhesive is used to bond double wall cups for hot beverages, the adhesive may have a ring and ball softening point of between about 180 ° F and about 300 ° F, more preferably between about 200 ° F and about 280 ° F, and most preferably between about 220 ° F and about 260 ° F, as determined by ASTM E28-99.

Hot melt adhesives can be applied to one or more substrates using a variety of application techniques. Examples include hot melt slot die (slot die) coating, hot melt wheel coating, hot melt roll coating, melt blown coating, and slot spray, spiral spray, and package spray methods such as methods for securing elastic strands. Spray coating techniques are numerous and may be carried out with or without the aid of compressed air which will shape the adhesive spray pattern. Hot melt adhesive materials are typically melt pumped through a hose to a final application point on a substrate.

In an embodiment of the invention, a method for forming a double-walled container comprises the steps of:

(a) applying the hot melt adhesive composition described herein in a molten state to the outer surface of a first generally cylindrical paperboard substrate;

In an embodiment of the invention, step (a) comprises applying the hot melt adhesive in a radial pattern. In other embodiments, steps (a) and (c) comprise applying the hot melt adhesive composition in the form of beads. Preferably, the paperboard is compostable. Still more preferably, the paperboard for the container is compostable and the container is a beverage cup. One such double-walled container is described in U.S. patent No. 6,109,518, which is incorporated herein by reference.

The compostable hot melt adhesives of the present invention may be used in a variety of applications, particularly where it is desired that the final article comprising the adhesive be compostable. As discussed above, embodiments of the adhesive of the present invention are particularly useful for double wall paperboard beverage cups. Exemplary other applications relate to box and carton applications, use with burlap or other compostable substrates for tree bulbs or plant seeds, and use with other compostable films. In each of these, the adhesive is applied to the first substrate in a molten state, then the second substrate (or a portion of the first substrate) is brought into contact with the adhesive, which is then allowed to cool and thereby bond the first substrate to the second substrate (or other portion of the first substrate that is folded over and stitched to the first substrate). For example, in one embodiment, tree bulbs or plant seeds may be wrapped in compostable burlap, an adhesive may be applied to the area of the split of the burlap, and the burlap is then folded onto itself such that the two split surfaces of the burlap are bonded to each other as the hot melt adhesive cools. In another embodiment, a first compostable film or substrate is contacted with an adhesive of the present invention, and then a second compostable film is contacted with the adhesive and allowed to cool, thereby bonding the two compostable films together to form a compostable laminate.

Inventive aspects

Aspect 1 is a hot melt adhesive composition comprising:

(a) polylactide homopolymers or copolymers;

(b) sulfonated copolyesters; and

(c) a plasticizer for the mixture of the components of the mixture,

wherein the binder is compostable.

Aspect 2. the composition of aspect 1, wherein the polylactide homopolymer or copolymer is selected from the group consisting of: polylactic acid; and copolymers of lactones, preferably glycolide and caprolactone.

Aspect 3. the composition of aspect 1, wherein the polylactide homopolymer or copolymer comprises, consists essentially of, or consists of polylactic acid.

Aspect 4. the composition of any of aspects 1-3, wherein the polylactic acid, the sulfonated copolyester, and the plasticizer are present in amounts effective to achieve at least 80%, preferably at least 90%, and most preferably 100% cohesive properties.

Aspect 5. the composition of aspect 4, wherein the polylactic acid, the sulfonated copolyester, and the solid plasticizer are present in amounts effective to achieve the bonding properties at a temperature of about 175 ° F, most preferably in a temperature range from 0 ° F to 175 ° F.

Aspect 6. the composition of any of aspects 1-5, wherein the polylactide homopolymer or copolymer and the sulfonated copolyester are present in a weight ratio of between about 1:1 and about 9:5 by weight, preferably between about 6:5 and about 8:5 by weight, and most preferably between about 13:10 and about 3:2 by weight.

The composition of any of aspects 1-6, wherein:

(a) the polylactide homopolymer or copolymer is present in an amount of between about 25% and about 43% by weight, preferably between about 30% and about 38% by weight, and most preferably between about 31% and about 37% by weight;

(b) the sulfonated copolyester is present in an amount between about 15% and about 35% by weight, preferably between about 20% and about 30% by weight, and most preferably between about 22% and about 28% by weight; and

(c) the plasticizer is present in an amount between about 5% and about 60% by weight, preferably between about 15% and about 55% by weight, more preferably between about 20% and about 50% by weight, and most preferably between about 36% and about 42% by weight.

Aspect 8. the composition of any of aspects 1-7, wherein the sulfonated copolyester is water dispersible.

Aspect 9 the composition of any of aspects 1-8, wherein the plasticizer comprises a solid plasticizer.

Aspect 10 the composition of aspect 9, wherein the solid plasticizer comprises benzoate.

The composition of aspect 11. aspect 10, wherein the benzoate ester is selected from the group consisting of: glycerol tribenzoate, sucrose benzoate, pentaerythritol tetraphenyl formate and 1, 4-cyclohexanedimethanol dibenzoate.

Aspect 12 the composition of aspect 10, wherein the benzoate ester comprises, consists essentially of, or consists of 1, 4-cyclohexanedimethanol dibenzoate.

The composition of any of aspects 1-12, further comprising a second plasticizer.

Aspect 14 the composition of aspect 13, wherein the second plasticizer is selected from the group consisting of: ethylene glycol, propylene glycol and polyethylene glycol.

Aspect 15 the composition of aspect 13 or 14, wherein the second plasticizer is present in an amount between about 1% and 5% by weight, preferably between about 1.3% and about 3% by weight, and most preferably between about 1.5% and about 2% by weight.

The composition of any of aspects 1-15, further comprising an antioxidant.

The composition of aspect 17. the composition of aspect 16, wherein the antioxidant comprises, consists essentially of, or consists of a hindered phenol.

Aspect 18. the composition of aspect 17, wherein the hindered phenol is selected from the group consisting of: 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene; pentaerythritol tetrakis-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate; n-octadecyl 3, 5-di-tert-butyl-4-hydroxyphenyl) propionate; 4,4' -methylenebis (2, 6-di-tert-butylphenol); 4,4' -thiobis (6-tert-butyl-o-cresol); 2, 6-di-tert-butylphenol; 6- (4-hydroxyphenoxy) -2, 4-bis (n-octylthio) -1,3, 5-triazine; di-n-octadecyl-3, 5-di-tert-butyl-4-hydroxybenzylphosphonate; 2- (n-octylsulfanyl) -ethyl 3, 5-di-tert-butyl-4-hydroxybenzoate; and sorbitol hexa [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ].

The composition of aspect 19. the composition of any of aspects 16-18, wherein the antioxidant is present in an amount between about 0.1% and about 1% by weight, preferably between about 0.25% and about 0.75% by weight, and most preferably between about 0.4% and about 0.6% by weight.

Aspect 20. the composition of any of aspects 1-19, wherein the composition comprises no more than 5 wt.%, more preferably no more than 4 wt.%, and most preferably no more than 3 wt.% of ingredients having a hydroxyl number greater than 100mg KOH/g.

Aspect 21. the composition of any of aspects 1-20, wherein the sulfonated copolyester has a weight average molecular weight between about 20,000 to 80,000g/mol, preferably between about 25,000 and 60,000g/mol, and most preferably between about 28,000 and 42,000 g/mol.

Aspect 22 the composition of any of aspects 1-21, wherein the polylactide homopolymer or copolymer has a melt index of at least 50, preferably at least 55, and most preferably at least 60g/10min using a 2.16kg weight at 210 ℃ according to ASTM method D1238.

The composition of any of aspects 1-22, wherein the binder meets the following two requirements: (1) decomposition test as defined by ASTM D6400-12 (using ISO 20200) and (2) aerobic biodegradation as defined by ASTM D6400-12 (using ASTM 5338-15).

Aspect 24. the composition of any of aspects 1-23, wherein the adhesive has a ring and ball softening point of between about 180 ° F and about 300 ° F, more preferably between about 200 ° F and about 280 ° F, and most preferably between about 220 ° F and about 260 ° F, as determined by ASTM E28-99.

Aspect 25. a method for forming a double-walled container, the method comprising the steps of:

(a) applying the hot melt adhesive composition of any one of aspects 1-24 in a molten state to an outer surface of a first generally cylindrical paperboard substrate;

Aspect 26 the method of aspect 25, wherein step (a) comprises applying the hot melt adhesive in a radial pattern.

Aspect 27 the method of aspect 25 or 26, wherein steps (a) and (c) comprise applying the hot melt adhesive composition in the form of beads.

Aspect 28 the method of any one of aspects 25-27, wherein the paperboard is compostable.

Aspect 29. a container formed by the method of any one of aspects 25-28.

Aspect 30 the container of aspect 29, wherein the paperboard for the container is compostable and the container is a beverage cup.

Examples of the invention

The following examples illustrate several aspects of certain preferred embodiments of the present invention and should not be construed as limiting the invention.

The feasibility of using the adhesive according to the invention for double-walled drinking cups was investigated. Specifically, the three formulations were tested for adhesive performance according to the following criteria.

The adhesive ingredients shown in table 1 below were mixed at room temperature and then heated. The molten adhesive was heated to 350 ° F and then applied as radial beads to the outer uncoated cardboard wall of the cup. The outer wall of a commercially available cardboard cup is adhered to the inner wall by piecing the outer wall with the adhesive that has just been applied to the inner wall. At a portion of the second wall that overlaps itself, another radial bead is applied to one of the split surfaces of the second wall, creating an axial strip. The second wall is then adhered to itself by splicing the splice surfaces of the axial strips. The radial beads (adhesive around the inner wall of the cup) create a gap between the inner and outer walls to provide thermal insulation. The adhesive was applied at 350 ° F using conventional adhesive application equipment.

The bond strength of the adhesive was measured by peeling the open end seal to check for 100% fiber tear (i.e., only the wall itself tears and the adhesive does not fail), and the heat resistance was tested by pouring hot water into the cup 1 minute after the adhesive was applied. The end seals must pass the test without delamination of the seals from top to bottom. Adhesive bond strength under 0 ° F and boiling water conditions compared to current conventional hot melt adhesives shown in the control.

As shown in table 1, the ingredient used was polylactic acid ("PLA") sold under the trademark Vercet a1000 by nyqi wacker inc; under the trademark Bostik, Inc

1831044 ("sulfonated copolyesters"); solid plasticizers sold under the trademark Benzoflex 352 by Eastman Chemical company (Eastman Chemical) ("solid plasticizers"); liquid plasticizers sold by the Dow Chemical company (Dow Chemical) under the trademark Carbowax Sentry PEG 400; and conventional antioxidants ("AO"). Table 1 lists the weights of the various ingredients (in orderIn grams). As shown, formulation 1 had about 30 wt% solid plasticizer. Formulation 1 failed the hot water test desired for this application. Formulation 2 (with more solid plasticizer than formulation 1, but no liquid plasticizer) also had very good adhesion immediately off-line and passed the hot water test compared to formulation 1. However, after 10 minutes at room temperature, the adhesive became brittle and failed adhesively in both radial and end seal applications. Formulation 3 passed the adhesive bond strength test both off-line and aged (1 day, 5 days, and 2 months at different temperatures of 0 ° F, 40 ° F, 72 ° F, 140 ° F, 160 ° F).

In addition, mixture 3 unexpectedly showed broader service temperature performance (0 ° F-160 ° F) and boiling water conditions (microwave 3.0 minutes, about 210 ° F water temperature). While formulations 1 and 2 do not meet the stringent requirements of this application (i.e., cups for hot beverages), these formulations may be suitable for other applications requiring compostable binders.

TABLE 1

Formulations	PLA	Sulfonated copolyester	Solid plasticizer	Liquid plasticizer	A0	Total of	Softening point
								1	39.1	20.6	30.3	10.0	0.5	100.5	206F
2	40.0	20.0	40.0	0.0	0.5	100.5	246F
								3	34.0	25.1	39.2	1.7	0.5	100.5	248F

An analysis was performed to determine if the adhesive composition of formulation 3 meets the requirements of the decomposition test (using ISO 20200) as defined by ASTM D6400-12. In particular, a drawdown film (draw down film) of this adhesive with a maximum thickness of 31.5mg was evaluated at 58 ± 2 ℃ for up to 84 days according to ASTM D6400-12 using ISO 20200. The compost material tested had a carbon to nitrogen ratio of 30:1, which was within the specifications of this test. At the start of the test, the pH of the compost material was about 7.0 and the total dry solids content was 44.5% when dried to constant weight at 105 ℃. The mature mushroom compost used in the tests was purchased from montreal Mushrooms, princeton, illinois, and as received had a C: N ratio of 13: 1. To meet this requirement, the samples tested must achieve a minimum of 90% weight loss within 84 days of testing. After 84 days, the tested adhesive samples were completely decomposed (100% weight loss).

An analysis was performed to determine if the adhesive composition of formulation 3 meets the requirements for aerobic biodegradation as defined by ASTM 5338-15. Specifically, ASTM D6400-12 mineralization was evaluated for adhesive samples exposed to aerobic biodegradation (tier two level testing) using ASTM D-5338-15 mineralization by contact with composting media at 58 + -2 deg.C. The tested laboratory compost had a C: N ratio of 29:1, which was within the specifications of this test. At the start of the test, the pH of the compost material was about 7.0 and the total dry solids content was 50.0% when dried to constant weight at 105 ℃. The mature mushroom compost used in the tests was purchased from montreal Mushrooms, princeton, illinois, and as received had a C: N ratio of 14: 1. To meet this requirement, the samples tested must achieve a minimum 70% carbon conversion in forty-five (45) days for mineralization according to ASTM D5338-15 and 90% carbon conversion in one hundred and forty-one (141) days for mineralization according to ASTM D5338-15. The tested adhesive samples met both requirements, including an average carbon conversion of 91.83% over 141 days.

Where a range of values is provided, it is understood that each intervening value, and any combination or subcombination of intervening values, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the recited range of values. Further, the invention includes ranges of ingredients that are the lower limit of the first range and the upper limit of the second range for such ingredients.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All publications and patents specifically mentioned herein are incorporated by reference in their entirety for all purposes, including describing and disclosing the chemicals, instruments, statistical analyses and methods reported in the publications that might be used in connection with the invention. Nothing herein is to be construed as an admission that the invention is not entitled to antedate such disclosure by virtue of prior invention.

Although illustrated and described herein with reference to certain specific embodiments, the present invention is nevertheless not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention.

Claims

1. A hot melt adhesive composition comprising:

(a) polylactide homopolymers or copolymers;

(b) sulfonated copolyesters; and

(c) a plasticizer for the mixture of the components of the mixture,

wherein the binder is compostable.

2. The composition of claim 1, wherein the polylactide homo-or copolymer is selected from the group consisting of: polylactic acid; and copolymers of lactones, preferably glycolide and caprolactone.

3. The composition of claim 1, wherein the polylactide homopolymer or copolymer comprises polylactic acid.

4. A composition according to claim 3 wherein the polylactic acid, the sulfonated copolyester, and the plasticizer are present in amounts effective to achieve at least 80%, preferably at least 90%, and most preferably 100% bonding performance.

5. The composition of claim 4 wherein the polylactic acid, the sulfonated copolyester, and the solid plasticizer are present in amounts effective to achieve the bonding properties at a temperature of about 175 ° F, most preferably in a temperature range from 0 ° F to 175 ° F.

6. The composition of claim 3, wherein the polylactic acid and the sulfonated copolyester are present in a weight ratio of between about 1:1 and about 9:5 by weight, preferably between about 6:5 and about 8:5 by weight, and most preferably between about 13:10 and about 3:2 by weight.

7. The composition of claim 3, wherein:

(a) the polylactic acid is present in an amount between about 25% and about 43% by weight, preferably between about 30% and about 38% by weight, and most preferably between about 31% and about 37% by weight;

(b) the sulfonated copolyester is present in an amount between about 15% and about 35% by weight, preferably between about 20% and about 30% by weight, and most preferably between about 22% and about 28% by weight; and is

8. A composition according to claim 1 wherein the sulfonated copolyester is water dispersible.

9. The composition of claim 1, wherein the plasticizer comprises a solid plasticizer.

10. The composition of claim 9, wherein the solid plasticizer comprises a benzoate.

11. The composition of claim 10, wherein the benzoate is selected from the group consisting of: glycerol tribenzoate, sucrose benzoate, pentaerythritol tetraphenyl formate and 1, 4-cyclohexanedimethanol dibenzoate.

12. The composition of claim 10, wherein the benzoate ester comprises 1, 4-cyclohexanedimethanol dibenzoate.

13. The composition of claim 1, further comprising a second plasticizer.

14. The composition of claim 13, wherein the second plasticizer is selected from the group consisting of: ethylene glycol, propylene glycol and polyethylene glycol.

15. The composition of claim 13, wherein the second plasticizer is present in an amount between about 1% and 5% by weight, preferably between about 1.3% and about 3% by weight, and most preferably between about 1.5% and about 2% by weight.

16. The composition of claim 1, further comprising an antioxidant.

17. The composition of claim 16, wherein the antioxidant comprises a hindered phenol.

18. The composition of claim 17, wherein the hindered phenol is selected from the group consisting of: 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene; pentaerythritol tetrakis-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate; n-octadecyl 3, 5-di-tert-butyl-4-hydroxyphenyl) propionate; 4,4' -methylenebis (2, 6-di-tert-butylphenol); 4,4' -thiobis (6-tert-butyl-o-cresol); 2, 6-di-tert-butylphenol; 6- (4-hydroxyphenoxy) -2, 4-bis (n-octylthio) -1,3, 5-triazine; di-n-octadecyl-3, 5-di-tert-butyl-4-hydroxybenzylphosphonate; 2- (n-octylsulfanyl) -ethyl 3, 5-di-tert-butyl-4-hydroxybenzoate; and sorbitol hexa [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ].

19. The composition of claim 16, wherein the antioxidant is present in an amount between about 0.1% and about 1% by weight, preferably between about 0.25% and about 0.75% by weight, and most preferably between about 0.4% and about 0.6% by weight.

20. The composition according to claim 1, wherein the composition comprises not more than 5 wt.%, more preferably not more than 4 wt.%, and most preferably not more than 3 wt.% of ingredients having a hydroxyl number of more than 100mg KOH/g.

21. The composition according to claim 1 wherein the sulfonated copolyester has a weight average molecular weight between about 20,000 and 80,000g/mol, preferably between about 25,000 and 60,000g/mol, and most preferably between about 28,000 and 42,000 g/mol.

22. The composition of claim 1, wherein the polylactide homo-or copolymer has a melt index of at least 50, preferably at least 55, and most preferably at least 60g/10min at 210 ℃ using a 2.16kg weight according to ASTM method D1238.

23. The composition of claim 1, wherein the binder meets both of the following requirements: (1) decomposition test as defined by ASTM D6400-12 (using ISO 20200) and (2) aerobic biodegradation as defined by ASTM D6400-12 (using ASTM 5338-15).

24. The composition of claim 1, wherein the adhesive has a ring and ball softening point of between about 180 ° F and about 300 ° F, more preferably between about 200 ° F and about 280 ° F, and most preferably between about 220 ° F and about 260 ° F, as determined by ASTM E28-99.

25. A method for forming a double-walled container, the method comprising the steps of:

(a) applying the hot melt adhesive composition of claim 1 in a molten state to an outer surface of a first generally cylindrical paperboard substrate;

26. The method of claim 25, wherein step (a) comprises applying the hot melt adhesive in a radial pattern.

27. The method of claim 25, wherein steps (a) and (c) comprise applying the hot melt adhesive composition in the form of beads.

28. The method of claim 25, wherein the paperboard is compostable.

29. A container formed by the method of claim 25.

30. The container of claim 29, wherein the paperboard for the container is compostable and the container is a beverage cup.